This week's massacre in Las Vegas brought one particular gun accessory into the spotlight. It's called the bump stock, and it's a device that some gun owners use to modify semiautomatic rifles to make them fire faster, almost as fast as a fully automatic rifle. Police say Stephen Paddock, the Las Vegas shooter, had a dozen bumps stock devices in his hotel room. They are legal, and they are widely available. Some lawmakers, though, from both parties are now asking whether that makes sense. North Country Public Radio's Brian Mann reports.

BRIAN MANN, BYLINE: Listen to people who collect guns and make guns a serious hobby, and you come across moments like this, a guy on YouTube - and there are lots of these videos - talking about the cool ways the rifle he's firing has been jacked up. The big feature is the bump, or slide, stock. It's like steroids for a rifle.

MANN: As the weapon bucks fast against the trigger finger, it dramatically accelerates the rate of fire. Machine guns and fully automatic rifles are really difficult for civilians to legally own in the U.S. They've been tightly regulated since the 1930s. But with this relatively easy and cheap modification, you can make rifles fire nearly as rapidly. Senator Dianne Feinstein has been trying to regulate guns she describes as assault weapons for years. Her last measure, in 2013, went nowhere. At a news conference yesterday, she introduced a new bill that would close what many Democratic lawmakers see as a flagrant loophole in America's gun laws.

(SOUNDBITE OF PRESS CONFERENCE)

DIANNE FEINSTEIN: Our bill is simple and straightforward - ban manufacturing or possession of accessories that accelerate a semiautomatic rifle's rate of fire to that of an automatic weapon.

MANN: She doesn't mention bump stocks by name. That's because there's a growing range of these devices available in stores and on the Internet - all legal, all designed to amp the fire rate of a semiautomatic rifle. Popular gun enthusiast Jerry Miculek posted this video of himself testing a hand-cranked device like a little Gatling gun.

(SOUNDBITE OF YOUTUBE VIDEO)

JERRY MICULEK: All right, let's see if we can light up this gizmo here. Here we go.

(SOUNDBITE OF GUN FIRING RAPIDLY)

MICULEK: (Laughter).

MANN: That crank device can be ordered online, fitting a semiautomatic rifle with a do-it-yourself kit with a price tag of just 40 bucks. Some Republican lawmakers who traditionally opposed nearly every gun control law now seem open to looking at these aftermarket kits. Oklahoma Republican Tom Cole spoke yesterday on MSNBC's "Morning Joe" reacting to the Las Vegas massacre.

(SOUNDBITE OF TV SHOW, "MORNING JOE")

TOM COLE: Well, when I heard the - saw the clips and heard the fire, I just assumed he had an automatic weapon. I did not know that there was technology capable, that cheaply, of transforming a semiautomatic into an automatic weapon.

MANN: Several Republican senators are now voicing similar concerns and say their staffs are investigating whether new legislation is appropriate. But Art Netherton, who runs a gun shop here in Las Vegas, says concerns about these devices are ridiculous.

Explain why somebody wants one.

ART NETHERTON: It is not for any nefarious purpose. You go out to the range. You go out to the desert out here, and you can shoot high speed and just have a good time with it.

MANN: That's part of the appeal. Some gun owners like tricking out their rifles, sort of like a hot rod car, comparing speed and power. They love the thrill of shooting fast. Modifying rifles with any of these devices is mocked by some gun enthusiasts. They say tweaked rifles buck and kick so much they're highly inaccurate. But manufacturers like Slide Fire, which makes one of the most popular bump stock kits equate their products with an act of patriotism, a way of supporting the Second Amendment. Here's a line from a Slide Fire promotional video.

(SOUNDBITE OF AD)

UNIDENTIFIED MAN #2: As long as patriots like you kindle its flame, freedom has but one enemy...

MANN: Slide Fire reportedly sold $10 million's worth of bump stock kits when they first went on the market six years ago. And some big national sporting goods chains like Cabela's have also been selling them. But after the Las Vegas massacre, Slide Fire abruptly suspended all sales. And Cabela's yanked bump stocks from its online catalog. The question now is whether Congress will go a step further and ban them outright.